#14101: Type synonyms can make roles too conservative -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.2.1 checker) | Resolution: | Keywords: roles Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: #8234 | Differential Rev(s): Phab:D3838 Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): comment:7 and comment:8 seem out of scope for this ticket. This ticket is about type synonyms, not type families. comment:7 seems utterly out of reach. As explained in the [http://repository.brynmawr.edu/cgi/viewcontent.cgi?article=1010&context=compsci_pubs paper], any type application that's not a declared parameter of a type is considered nominal. I think we'd need to overhaul the roles design to get that. comment:8, though, seems approachable, in two steps. Step 1: use data families, not type families. Step 2: #8177, which will allow non-nominal roles on data families. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14101#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler